Engadget reviews the Pogoplug, a simple box that turns any USB hard drive into a networked device, accessible from even the wild yonder of the internet:
All-in-all, we like the Pogoplug a lot, but we do have a couple of quibbles. Mainly, we wish this were a WiFi enabled device, which would spare some cables and setup pain. Additionally, it would be nice to see a device of this nature with multiple USB ports instead of just the one -- yes, you can attach a hub, but you're already dealing with a mess of lines as it is. Still, for $99, the ability to turn a random drive into not only a network-accessible device, but a remotely-accessible device is huge, and we plan on putting it into heavy rotation around here.
Update: Here's another one, called the SheevaPlug, that isn't out yet. It looks so similar I wonder if it isn't the same basic product being rebadged twice.